1. Field of the Invention
The present invention relates in general to a color wheel, and in particular to a color filter assembly having excellent balance and stability of rotation by adjustable and thus enhanced static mass balance.
2. Description of Related Art
Referring to FIGS. 1a and 1b of the attached drawings, a conventional color wheel comprises a carrier 11, a color filter 12, and a motor 2. The color filter 12 is fixed to the carrier 11 by adhesive 13, wherein the carrier 11 and the shaft 22 are connected and secured at the center of the motor 2 with a cover 21. The motor 2 rotates the carrier 11 and the color filter 12 around central axis 10 via the shaft 22.
As shown in FIG. 1b, the conventional color filter 12 has three filter segments 12a, 12b, and 12c. A recess 18 is formed on the carrier 11 to compensate unbalanced mass thereby providing stable rotation. It is difficult to precisely form the recess 18 however, and unbalanced mass distribution may occur, for example, due to flow of adhesive 13. Hence, stable and balanced rotation is difficult to achieve in the conventional color wheel.
Other prior arts are known. U.S. Pat. No. 6,011,662 disclosed a color wheel, comprising a plurality of color changing elements each fixed to a hub by pegs on opposite sides. The pegs, although changing the mass center of the color wheel, do not construct to enhance mass balance statically or dynamically, because the position of each peg is fixed on the color wheel, and is thus not adjustable.
U.S. Pat. No. 5,777,694 discloses a color wheel comprising a plurality of color filter segment fixed by a two-piece hub. The hub is made thicker at a middle portion and this makes the hub “mass-loaded” around a drive shaft for mass balance. However, no adjustability of the mass balance is provided in the known device, not to mention using position-adjustable elements to effect precisely mass balance.
JP Patent Document No. JP2001023290A discloses a turntable comprising a plurality of radially movable balls. When the turntable rotates, centrifugal forces move the balls with respect to the turntable to effect dynamic balance of mass. However, the balls do not provide static balance for their positions cannot be fixed with respect to the turntable.
Thus, the present invention is aimed to effect a precise static balance of mass for a color wheel in order to enhance rotation stability thereof.